Such a printed circuit board (PCB) may be classified into a single-layer PCB and a multi-layer PCB, such as a build-up board.
The build-up board, that is, the multi-layer PCB is manufactured one-layer by one-layer and the quality of the multi-layer PCB is evaluated to improve the product yield of the multi-layer PCB. In addition, interconnection lines are precisely connected to manufacture a high-density and small-size PCB. According to the build-up process, interconnection lines are formed between layers to connect the layers to each other through via holes formed in the layers. Instead of a mechanical drilling work, a laser process is performed to form the via holes having a micro size.
FIG. 1 is a sectional view showing a multi-layer PCB according to the related art.
Referring to FIG. 1, the multi-layer PCB 10 according to the related art includes a core insulating layer 1, inner circuit pattern layers 3 and 4 formed on and under the core insulating layer 1, upper and lower insulating layers 5 and 6 burying the inner circuit pattern layers 3 and 4 and outer circuit pattern layers 7 and 8 formed on the upper and lower insulating layers 5 and 6, respectively.
A conductive via 2 and conductive via holes are formed in the core insulating layer 1 and the upper and lower insulating layers 5 and 6 to electrically connect the inner circuit pattern layers 3 and 4 to the outer circuit pattern layers 7 and 8.
The multi-layer PCB 10 having the above structure according to the related art can be manufactured by forming even circuit pattern layers (four layers are shown in FIG. 1). After depositing insulating layers, two layers serving as outer layers are electrically connected to each other through the drilling work or the laser process. However, since the number of the circuit pattern layers is limited to the even number, a thickness of the substrate may be increased, so that the multi-layer PCB 10 may not be applicable for the portable electronic appliances or the substrates having the light and slim structure, such as semiconductor chips.